How can I mess with these displays if I get a Raspberry Pi and maybe Kali. What sort of things can I do? Preferably replace the image with a protest message.
The technical aspect of it shouldn’t be an issue but I’m just struggling for ideas really and some insight into how they operate.
If we are talking about road side billboard style advertisements then I expect those to be cellular.
You will probably have to do some searching on shodan to find the devices.
If I were them I shouldn’t allow remote access and only do a pull from the devices. But who knows.
If the signage is outside of a company I’d expect that to just be hardwired and running from something simple like an hdmi extender from an office computer.
Likely a felony and as you are asking here you’ve neither the knowledge nor experience to risk such.
Black clothing, bricks and some matches